refactor: fix the testing src-layout structure and use relative imports

[tonyandrewmeyer]

The original commit merging ops-scenario into this repository had an error in the src-layout structure: the src folder should contain a folder for each of the importable packages, not have all of the individual modules.

This PR moves everything in testing/src/ to testing/src/scenario/ to fix this. This means that the build tool can find the package without any help, and makes editable installs work correctly, which removes a quirk in the tox dependency installs. It also makes it simpler to work on the project, since the ops and scenario packages are available in the expected format with the expected name (although src-layout encourages editable installs for development).

For the second part of the cleanup, the PR changes the testing/src/scenario imports to be relative for everything inside of that location. While adjusting these, most of the imports are adjusted to import from the top-level ops namespace rather than from individual modules (except for non-exported names).

[benhoyt]

Oh, this is a pity, as it means the code is (even) more nested. I guess it can't be just testing/*.py or scenario/*.py, because they're two different PyPI packages and need their own pyproject.toml?

[tonyandrewmeyer]

Oh, this is a pity, as it means the code is (even) more nested. I guess it can't be just testing/*.py or scenario/*.py, because they're two different PyPI packages and need their own pyproject.toml?

We could go to a flat layout, which would remove the src layer (so instead of moving everything to src/scenario it would be renaming src to scenario). My understanding is that src-layout is considered best practice these days, but I don't have strong feelings about it.

[dimaqq]

getting rid of "scenario" all over the source code is a win :)

[dimaqq]

./testing/. looks funky, but I wonder if this notation is required.

[tonyandrewmeyer]

./testing/. looks funky, but I wonder if this notation is required.

It can't be testing (because that would look for a package on PyPI called "testing"). ./testing and testing/. both work for me, at least with uv pip. I don't have a strong preference here - would you prefer either of those?

[tonyandrewmeyer]

Actually, now that -e is there, testing would work because the -e forces it to be a local reference since you can't have an editable PyPI install.

So it could be -e testing if you prefer that? There's a small risk that someone drops the -e or similar and causes problems in the future, but I think testing is a restricted PyPI name anyway, so people can't actually register something bad under it.